Tuesday 3 November 2009

Millipedes

There are around 8000 different species of millipede in the world, of which 52 are present in the UK. The name 'millipede' translates as ‘thousand legs’, and although these creatures are indeed many-legged none of them quite reach the thousand mark, with 750 being the record (held by Illacme plenipes of the USA). Their bodies are made up of multiple segments, most of which carry two pairs of legs and are protected by a chitinous cuticle. The different segments are connected together by ball and socket joints, allowing the creatures to be incredibly flexible, and they will often curl up into a compact spiral if they sense that a predator is nearby.

Despite all those legs millipedes are rather slow-moving in comparison with similar critters. They are herbivores and therefore have no need to chase prey, preferring to spend their time burrowing through the leaf litter and chomping on the decaying vegetable matter that is highly unlikely to run away. This lack of speed does put them at a disadvantage when escaping from predators, and so as well as employing the tactic of coiling up they can emit unpleasant chemicals such as hydrogen cyanide in order to make themselves less palatable. Despite this defence other creatures do manage to eat them; they are at risk from frogs, toads, some spiders and birds. Starlings seem to find them especially tasty - millipedes can make up half of their diet in the spring.

I have recently spotted two different species of millipede. The first, shown above, was hanging out on a shady crag close to a forest in Northumberland, at a rather higher altitude than they would usually be found. This was a White-legged Snake Millipede, a common species that can grow to about 5 cm long. The second, shown below, was much smaller, barely more than a centimetre in length, and at first glance I thought it was a woodlouse. Its very shiny body and evenly-sized segments however proved it to be a Pill Millipede, a less common species whose party trick is rolling up into a tight ball. I found it on a beach on Anglesey, not its most usual habitat by any means. It is much more likely to be found, like the others, in woodland and on rough pasture where there are more tasty dead leaves to munch on.

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